Various types of inserters have been developed for the positioning of mechanical and copper wire-containing intrauterine devices (IUDs) as well as of intrauterine systems having a drug containing cylinder (IUSs). In the following, IUD and IUS can be used interchangeably and when one is mentioned, it is to be understood that either of them can be used. Simple rod-shaped inserters have been suggested for inserting relatively small or sufficiently flexible intrauterine devices in their original, expanded shape by using simple push-in technique. However, most common inserters are constructed for introducing the device into the uterus in a contracted state. These inserters usually comprise an insertion tube having a relatively narrow diameter and a rounded, blunt end which will pass through the cervical canal easily and will not damage or injure the fundus upon contact therewith, and a plunger inside the insertion tube. Prior to insertion the device, whether an IUD or an IUS, is usually retracted into the insertion tube either by means of string(s) attached to the device and intended for the removal of the device from the uterus, or by pushing the device into the insertion tube by a plunger with inserters having a special window to adapt the device in the expanded shape (see for example GB 1 403 393). Then the insertion tube with the device therein is introduced through the cervical canal into the uterus. When the device is correctly positioned, it is released either by pushing the plunger towards the uterus or by holding the plunger steady and by retracting the insertion tube outwards. Once expulsed from the insertion tube within the uterine cavity, the device is supposed to resume its original expanded shape.
A typical example of an intrauterine device has a T-shaped body fabricated of plastic material and consisting of an elongated body part having at one end a transverse member comprising two wings, the elongate member and the transverse member forming a substantially T-shaped piece when the device is in the expanded configuration, for example positioned in the uterus. The tips of these wings are preferably hemispherical in order to facilitate the introduction of the device through the cervical canal. The elongate member has a copper spiral or wire or a hormone capsule arranged around the body. The end of the vertical body part has a loop with a string or strings attached to it, with which the device can be removed from the uterus after use or whenever needed.
The diameter of the elongate member in intrauterine systems having a drug containing cylinder is greater than in copper wire-containing IUDs or mechanical devices, and thus the diameter of the insertion tube also has to be larger. However, the frames of these intrauterine systems, or in the commonly used T-shaped systems the hemispherical ends of the transverse member, are small in relation to the diameter of the insertion tube. Therefore the correct positioning of the IUS within the insertion tube is extremely important, and this will only be attained by properly handling the removal string(s) during the preparatory steps and insertion as well as when finally releasing the IUS after insertion. Challenging steps, which will be exemplified with a common T-shaped device, apply as well to intrauterine systems having another type of frame, for example 7-shaped or closed, continuous frames.
For the insertion of a T-shaped intrauterine system it is extremely important that the hemispherical ends of the transverse member are in the exactly correct position in relation to the edge of the insertion tube at the moment of introducing the device in the uterus. If the IUS is pulled into the insertion tube by means of the removal string, which is usually the case with the existing devices, it is understandable that it is difficult to make the IUS stop in the correct position, especially if the relative movement of the insertion tube and the plunger is not restricted by any stop member. Pulling with too much force easily makes these ends enter almost completely into the insertion tube. During the insertion of the device, the sharp edges of the insertion tube may interfere with the introduction of the device through the cervical canal. On the other hand, if the device is not drawn deep enough into the insertion tube, the frame ends project outwardly because of a relatively wide insertion tube. The diameter at the level of the wings remains too wide, which makes the introduction of the device more difficult. It is easier to make the wings stop in the correct position in the case of copper-wire devices, because then the insertion tube is narrow in relation to the wings and therefore there is no risk of the wings being drawn too deep into the tube even by forceful pulling.
When the device is pulled into the insertion tube, it is important that the device is directed onto the plunger in the correct position, i.e. without damaging the loop, the rest of the body or the string(s). If the device is pulled onto the plunger in a wrong position, the edges of the insertion tube or the plunger can damage the loop or the body. If pulling is continued and the device does not turn into the correct position, the string(s) will finally cut through the loop or the body, which can also cause the device to get jammed within the insertion tube or plunger.
The European patent application EP 1 691 740 relates to an inserter, with which the correct positioning and directional stiffness of the device in the inserter prior to and during insertion can be ensured, for instance, by shaping the forward end of the plunger such that the IUS assumes a specified constant configuration when drawn into the insertion tube. The IUS will thus not be twisted during insertion.
European patent EP 798 999 relates to an inserter, which allows the correct positioning of an IUS also in those cases in which the elongate member of a T-shaped device contains active material, which involves a diameter larger than that of an elongate member of a copper-wire IUD. The inserter comprises a plunger, a handle attached to the plunger, a string for the removal of the IUS, a cleft on the end of the handle to lock the string(s) in such a way that the IUS remains immobile in relation to the plunger, and an insertion tube around the plunger. The IUS is drawn into the insertion tube by pushing the tube over the device or by pulling on the removal threads whereafter the threads are manually locked in the cleft. The relative movement of the plunger and the protective tube is restricted by a stop member or stop members to ascertain that the correct configuration of the IUS is achieved. The stop members ensure that the front edge of the insertion tube is stopped in a configuration in which the hemispherical tips of the T-wings remain partly uncovered by the insertion tube but the wings nevertheless remain pressed against each other. This inserter overcomes many of the problems encountered with the conventional inserters, but the string(s) still need to be manually handled and locked.